It is well known that a variety of packaged electronic devices require moisture protection to achieve a specified operating or storage lifetime. In particular, the relative humidity within the encapsulated packages of highly moisture-sensitive electronic devices, such as organic light-emitting devices (OLED), polymer light-emitting devices, charge-coupled device (CCD) sensors and micro-electro-mechanical sensors (MEMS), must be controlled below a certain level, particularly below 1000 ppm or even in some cases below 100 ppm, in order to fully protect the organic light-emitting layers, electrodes, or other moisture-sensitive components.
There are several approaches used in the prior art to protect encapsulated or packaged devices from water. These techniques do not always work: organic sealants may not meet the stringent moisture permeation requirement; moisture impermeable solder sealants may have melting temperatures that are too high for temperature sensitive devices; and desiccant packages attached on the device inner wall may block light emission out of the device, a particular problem for top-emitting organic light-emitting diodes.